175

Impact of Global Climate Change on Agriculture
and Food Security over Asia
Motoki NISHIMORIDivision of Agro-Meteorology,
National Institute for Agro-Environmental Sciences
3-1-3, Kan’nondai, Tsukuba, Ibaraki 305-8604, Japane-mail: mnishi@niaes.affrc.go.jp

Abstract
The current and latest works on the impacts of global climate change on agricultural production
throughout the Asian region are introduced from the viewpoint not only of changes in natural environment (meteorological and water resources) but also of soil environment changes and increased insect
pests. The results involve a model simulation of rice yields at different locations in Asia under increased
CO2 and temperature conditions. How the impact of global warming on the agro-ecosystem may influence food security in Japan and around the world is also discussed.
Key words: agriculture, global climate change, rice, soil water content

1. Introduction
According to the Third Assessment Report ofWorking Group I of the International Panel on Climate
Change (IPCC, 2001a), the global averaged surface airtemperature has increased by about 0.6°C over the last
100 years. Comparing this temperature increase
among various parts of the globe shows that the greatest increase has occurred in northern and eastern Asia,
where average temperature rose almost 1°C. If thistrend continues, agriculture in East Asia may become
the first to suffer the negative effects from global
warming. In fact, there have been many cases ofsevere weather and natural disasters such as heavy
rainfall in the rainy season, repeated landfalls of many
typhoons and heavy snowfall in Japan in recent years.
Variations in wet and dry environments in China havealso been predominated such as the loss of water in
the Yellow River, the remarkable drought of 2003 in
the northeastern region and severe flooding in 1998 in
the Yangtze River. Thus, the recent climate seems tobe similar to that projected by the IPCC under future
global warming or unusual weather scenarios.
Agriculture in China, which is one of the world’s
major food producing and consuming countries, hasbeen affected not only by changes in the natural environmental change but also by rapid economic growthand explosive population increases. Production ofmajor crops (wheat and maize) in most parts of China
has depended on rain-fed water supplies, so it isvulnerable to year-to-year climate variation, especially
Global Environmental Research
10(2)/2006: 175-179
printed in Japanto changes in precipitation. In addition, the amplitudeof the variation in agricultural production has tended
to increase. Elucidating the causal factors and evaluating the future impacts due to climate change are crucial tasks with regard to ensuring a stable food supply
in East Asia, and hence, food security around theworld.
The present paper will focus on risks to agricultural production related to temperature and CO2 rises
and changes in water resources in East Asia. It will
examine a few of analytic studies on climate change
impacts on natural environments and growth inhibition factors in relation to changes in Asian foodproduction. It will also introduce a crop simulation
model of the physiological and ecological effects oftemperature and CO2 rises and a statistical model
study on changes in agricultural production taking
trade and economics factors into consideration.
Further, it discusses how such climatic impacts on
Asian agro-ecology may affect world food security
from the viewpoint of changes in precipitation andland productivity and the effects of trade and markets.

2. Vulnerability of Rice Production of Japan
Generally, there are three approaches to projecting
future changes in rice production as follows:
1. To project them in terms of statistics, based onchanges in previous production, and inputting future climate (temperature, etc.) change predictions,
2. To cultivate rice in environments with higher tem©2006 AIRIES176

M. NISHIMORI

perature and CO2 levels,
3. To project changes by using computer simulation
models from seeding to harvesting.
These three methods have their own separate advantages and disadvantages. It is possible to consider
the influence not only of high temperatures but also of
insect pests and water resource shortages in spring due
to earlier snowmelt, and to set up various other subjects in Method 1. Method 1, however, is based only
on statistical calculation and cannot take socioeconomical and political matters into consideration.
Method 2 provides the possibility of estimating actual
rice yields at projected future temperature and CO2
concentrations. It is difficult, however, to run experiments applying these conditions to the various speciesof rice and soil conditions all around the world and it
is insufficient for getting information on complicatedeffects of temperature and CO2 concentrations, andtheir differences among rice species.
Paddy rice production in Japan is often affected bycool summers and high temperatures, which damage
the crops. In order to project the future rice productionof Japan under climate change or global warming, it isnecessary to clarify quantitatively the influence ofchanges in climate factors such as air temperaturesand solar radiation on rice yield. Therefore, a multiple
regression analysis was conducted to examine changes
in rice yields, using averaged air temperature andaccumulated solar radiation during the heading period
in each agricultural region (Nishimori & Yokozawa,
2001). In addition, obstructive factors such as pests
and diseases or water resource shortages should beconsidered in estimating the vulnerability of rice production (Nishimori et al., 2007). In the northern partof Japan, the rice yield is generally increasing as thetemperatures rise and the diurnal temperature range

Fig.1 Estimated increase in the yield loss of rice caused by
C. suppressalis under global warming.
R: predicted annual yield loss in the period from 2031 to 2050
divided by the corresponding loss in the period from 1981 to
2000. (Yamamura et al., 2006)(DTR) decreases. In the western part of Japan, on theother hand, the rice yield is generally increasing as
solar radiation increases. In the Hokuriku region andnorthwestern parts of Kyushu, the rice yield is relatively sensitive to high temperatures so the risk ofhigh temperature injury is recognized. The above
vulnerabilities to climate factors, as well as those topests, diseases and water resource shortages were included. As a result, rice production in the Hokuriku
region was found the most vulnerable to CO2-induced
high temperatures. Rice production in the Sea of Japan
coastal part of the Tohoku region and the northwesternpart of Kyushu is also vulnerable (Nishimori et al.,2007).
Considering the impact of insect pests on rice production, Yamamura et al. (2006) have calculated thefuture average yield loss due to insects relative to that
expected in a normal year by substituting future projected temperatures. Figure 1 shows that the yield loss
resulting from the insect pest species, rice stem borer
Chilo suppressalis (Walker) (Lepidopotera: Pyralidae),in the period from 2031 to 2050 will exceed that in the
period from 1981 to 2000 by a factor of about 1.6 inmost areas of Japan and about 1.8 in the Hokuriku
region. This result demonstrates that climate change
impact research on rice production in Japan has madesignificant progress relative to the period when riceproduction change was discussed only from the viewpoint of high temperatures and increased CO2.

3. Vulnerability of Rice Production
throughout Asia
The IPCC Working Group II has pointed out that
Asian agriculture and food security faced crises due tothe increase in severe high temperatures, flooding, sealevel rise and strengthened tropical storms (IPCC,
2001b). In this section, a moisture balance model forsoil was introduced in order to evaluate the vulnerability of cereal production in China and a growth simulation model was introduced to explain crop growth
processes under various Asian environmental conditions. The latter modeling analysis corresponds to thethird method as described in Section 2.
Results of a spatial-temporal analysis of the soil
moisture environment during the past 50 years
throughout China are shown in Fig. 2. Figure 2(a)represents the ratio of normalized soil moisturechanges during 1976-1995 to that during 1946-1975,
and Fig. 2(b) shows the significance of the difference
using a double-sided student-t test. The normalized
soil moisture was found to have decreased maximallyby 10 mm in the North China Plane involving Hebei,
Henan and Shandong Provinces and a part ofnortheastern China (Fig. 2). The agricultural water
demand in southern China is projected to decrease
generally, and the cropland soil-moisture deficit todecrease due to climate change. However, in northern
China, the agricultural water demand is expected toImpact of Global Climate Change on Agriculture and Food Security over Asia

increase, and the soil-moisture deficit to increase
generally. Such changes in the water resources would
have consequent impacts on the yield index (Tao et al.,2003). Cropland surface runoff during the growing
period is expected to increase on some sloping
croplands in the southwestern mountainous areas andin some areas along the south coast. These changes
would have important implications for agricultural
production. Particularly the rain-fed crops in the North
China Plain and northeastern China would facewater-related challenges in the coming decades due tothe expected increases in water demands andsoil-moisture deficit, and decreases in precipitation.
What should be of concern is that the rain-fed crops in
the North China Plain and northeastern China could
face water-related challenges in coming decades dueto the expected increases in water demands andsoil-moisture deficit, and decreases in precipitation.
The effective adaptation options should include
adjusting the inharmonious proportion between
plantation, forestry and stockbreeding, improving
greatly the water use efficiency in agriculture andincreasing the water supply to northern China (Taoet al., 2003). The reason for the decreasing tendency istemperature rises and the related increase in evaporation. The range of year-to-year variation has decreased
in regions affected by dryness, and the surface run-off

177

rate over the Yellow River area has been decreasing.
Furthermore, the future (2031-2065) projected soil
moisture compared with the current one (1961-1995)
shows that soil moisture could increase in South
China and decrease in the northern upland area ofChina (Yokozawa et al., 2001).
Next, growth and yield simulations were introduced for different rice genotypes grown under
700 µmol/mol CO2 (doubled CO2) and different degrees of temperature rise at the respective sites of the
Asian Rice Network Experiment (ARICENET: Horieet al., 2003). This crop growth and productivity prediction model for rice considers procedures for selecting species, changing crop calendars and applying
mitigation techniques. This new rice model was also
developed to simulate growth and yields of different
genotypes under variously different environments.
The model simulation makes it possible to project rice
yields at different locations in Asia under increased
CO2 and temperature conditions, and to discuss theimplications of the simulation results for future Asianrice production.
Figure 3 represents the simulation results for cultivars of IR72 (indica) and Nipponbare (japonica) in
Iwate and Kyoto in Japan, Nanjing and Yunnan in

(a)

(b)

Fig. 2 (a) Geographical distribution of change in normalized
soil moisture (ratio of annual mean soil water content
to soil water capacity in crop root zone) in China
during the period of 1976 - 1995 to that of 1946 - 1975
and (b) geographical distribution of the significant
level of the difference of the soil moisture between
above two periods. (Yokozawa et al., 2001)

Fig. 3 Percentage yield change from the current conditions ofless than 700 umol/mol (CO2) with 0°C, 2°C and 4°C
temperature rises, simulated for cultivars IR72 andNipponbare in Iwate and Kyoto in Japan, Nanjing andYunnan in China, and Ubon Ratchathani in Thailand.
Climate data of 2001 and 2002 at each location wereused as base climate. (Horie et al., 2005)

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M. NISHIMORI

China, and Ubon in Thailand as a percentage yieldchange from the base conditions at each site (Horieet al., 2005). The results on IR72 in Iwate andNipponbare in Ubon are not shown in Fig. 3 because
these cultivars showed very poor adaptability to theclimates of those sites. The model projected higher
yield responses to elevated CO2 in IR72 (indica) thanin Nipponbare (japonica) simulated at all the locations
under the current temperature conditions, which
agrees well with the observations. Since the model
assumed the same leaf photosynthetic response to CO2
for both genotypes, the higher yield response of IR72
to CO2 was due to its larger sink forming ability andhigher source limitation under ambient CO2 than
Nipponbare. The model projected that doubled CO2
alone will increase the yields of the two genotypes by
about 20%-30% at most locations simulated. Thiseffect of CO2, however, was drastically reduced by a
2°C temperature increase at all locations except Iwate
in the northern part of Japan. In Kyoto, where summer
temperatures are much higher, doubled CO2 with a
2°C temperature rise would significantly reduce theyield of Nipponbare, reflecting the increased spikelet
susceptibility to high temperature damage under conditions of elevated CO2. It was projected that doubled
CO2 with a 4°C temperature rise would have severely
negative effects on rice yields at most Asian locations
except for northern areas like Iwate. The negative effects were more pronounced in warmer areas like
Ubon. The results in Ubon in Fig. 3, however, were
for wet-season rice, and severely negative effects on
dry-season rice yields were projected there under conditions of doubled CO2 with a temperature rise of
more than 2°C (Horie et al., 2005).

4. Food Security in Japan
There are many kinds of works projecting changes
in future food production, but there is a strong need toconsider the effects of markets and trade worldwide
added to the three above-described methods, using
techniques such as cultivation experiments, statisticalanalyses and crop modelings. The two representative
examples are CERES-Wheat, a crop model, and an
integrated model connected to the world food trademodel, BLS (Parry et al., 1999). In Japan, the sameprocedure (Furuya & Koyama, 2005) has been appliedby the Japan International Research Center for Agricultural Sciences (JIRCAS). The Japanese modelutilized a non-linear process that estimated crop yield
as a function of time, temperature and precipitation.
Figure 4 represents one example by using theJapanese model, a comparison of production in twocases of four major crops (wheat, maize, rice andsoybeans) and other grains between the future (2025)
and current (2005) situations, which consider only
economical effect and together with the effects ofrising temperature around the world. These results
show that world grain production may tend to increase

Fig. 4 Comparison of two cases of changes in production offour globally major crops (wheat, maize, rice andsoybeans) and other grains between future (2025) andcurrent (2005) situations, considering only economical
effect (Left: Light) and together with the effects ofrising temperatures around the world (Right: Dark).
(Furuya & Koyama, 2005)

gradually. This means that demand could potentiallybe met in the world. Wheat, the biggest crop, may
continue to show increased yields in the countries
with highest productivity such as the United States,
India and China.
Considering the effects of climate change effect,
major crops other than rice have not shown changes in
the productivity because this model has a definition ofactive trade related to supply and demand. For riceproduction, however, a relative decrease in productivity was found as the result of higher temperatures. The
reason is the world’s rice production and consumption
is clustered in the Asian region in comparison withwheat, which is in demand and traded throughout theworld. Actually, in Japan, however, the consumptionof rice has significantly decreased compared with thedecreasing of production though rice imports from the
U.S. or Australia have been increasing considerably.
Therefore, a crisis in the supply and demand for ricein Japan is not expected in the near future. The othermajor grain in Japan, wheat, is dependent on imports
from abroad. There is concern about how Japan could
supply wheat demand if imports were stopped. Actually, wheat can be produced at lower temperatures andless precipitation areas compared with rice, and has
been cultivated even areas of limited growth. According to the results in Fig. 4, the productivity of wheat is
not expected to be affected by global warming, but themodel analysis used in Fig.4 has a problem of not considering future changes in precipitation.

5. Summary and Discussion
Future vulnerability of rice production in Japan has
been previously indicated only with regard to hightemperature damage, but now there is a tendency tounderstand influences of insect pests and water resource shortages due to decreasing snow cover. For
example, this paper points out that the decrease in riceproduction due to insects may occur by a factor ofImpact of Global Climate Change on Agriculture and Food Security over Asia

more than 1.8. From the viewpoint of previous variability and future projection of water resources, thispaper also reports on significant dryness in China
where the average soil moisture has decreased maximally by 10mm in the North China Plane, involving
Hebei, Henan and Shandong Provinces and a part of
the northeastern plane.
According to crop simulation model analyses, doubled CO2 at current temperatures contributed by a factor of 1.2 to 1.3 to the current usual yield in all analyzed stations in Asia, but doubled CO2 with 2°C of
temperature rise eliminated the good effect. In addition, doubled CO2 with 3°C or more of temperaturerise caused a decrease in yields, except in Iwate. Thiseffect was more prominent for tropical dry season cultivation or in Kyoto and Nanjing where summer temperatures are significantly higher. Thus it is found that,
under conditions of increased CO2, species whichhave large numbers of spikelets have generally an advantage for production, but a 2°C temperature risedenies the fertilization effect of CO2 and a 4°C warming is connected to decreased rice yield. We have to
pay attention to the fact that bad influence of risingtemperatures and CO2 levels are larger in temperatezone areas with hotter summers like Kyoto andNanjing and in tropical areas with dry-season cultivation, therefore, the currently projected climate change
could have a remarkable influence even with consideration of species of rice and crop calendar mitigation
efforts.
Agriculture worldwide generally depends on precipitation, and water resources are absolutely necessary for agriculture. Actually, water resources areneeded not only for agriculture and tap water but also
for every situation of human life, but water resources
face a crisis due to climate change or various politicaland economical issues. We often hear the phrase “the21st century is an aqueous century”. In addition, we
can say, “the 21st century is an agricultural century”
for the above reasons.

Acknowledgment
The main results of this paper were supported by
the Global Environment Research Fund, B-11: Assessment of impacts, adaptation and vulnerability of natural ecosystems to global warming; (4) Studies on therisk assessment of agricultural ecosystems to global
and regional climate change and variability, provided
by the Ministry of the Environment of Japan. This research work was conducted by Drs. Masayuki
Yokozawa, Yasuto Shirato and Ichiro Taniyama of the
National institute for Agro-Environmental Sciences,179

Prof. Yousay Hayashi of the University of Tsukuba,Prof. Takeshi Horie (present affiliation: National Agriculture and Food Research Organization) and Ms.
Hiroe Yoshida of the University of Kyoto and Prof.
Hiroshi Nakagawa of Ishikawa Prefectural University,
along with the author. The author thanks them for theirgreat effort.
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(Received 13 November 2006, Accepted 18 December, 2006)